PCV-2 is linked to the post-weaning multisystemic wasting syndrome (PMWS) observed in young pigs. This disease was encountered for the first time in Canada in 1991. The clinical signs and pathology were published in 1996, and include progressive wasting, dyspnea, tachypnea, and occasionally icterus and jaundice.
Nayar et al., Can. Vet. J. Volume 38, June 1997 detected porcine circo virus in pigs with clinical symptoms of PMWS and concluded that a PCV, other than the known PCV recognized as a natural inhabitant of PK-15 cells, could be linked to PMWS. Later publications (Hamel et al., J. Virol., 72(6), 5262-5267, 1998; Meehan et al., J. gen. Virol., 79, 2171-2179, 1998) confirmed these findings, and it was proposed (Meehan et al., supra) to refer to the new pathogenic PCV as PCV-2, whereas the original PK-15 cell culture isolate (Tischer et al., Nature 295, 64-66, 1982), should be referred to as PCV-1. PCV-2 is a small (17-22 nm) icosahedral non-enveloped virus containing a circular single stranded DNA genome. The length of the PCV-2 genome is about 1768 bp. PCV-2 isolates originating from different regions in the world seem to be closely related to each other and display 95 to 99% nucleotide sequence identities (Fenaux et al., J. Clin. Micorbiol., 38(7), 2494-2503, 2000). ORF-2 of PCV encodes the capsid protein of the virus. The ORF 2 of PCV 2 encodes a protein of 233 amino acids. The ORF 2 of all PCV-2 isolates share 91-100% nucleotide sequence identity and 90-100% deduced amino acid sequence identity.
A conventional vaccine to prophylactically treat animals, in particular pigs, against an infection with pathogenic porcine circo virus type 2, may be based on whole PCV-2 virus as (non-replicating) immunogen. However, in the case of PCV-2 matters are complicated by the fact that PCV-2 does not replicate to high titers in cell culture. A vaccine based on whole virus as the immunogen is therefore less ideal from a practical (economic) point of view. In the art it has been shown that the ORF2 encoded capsid protein (even when recombinantly expressed) is suitable as a subunit immunogen of porcine circo virus type 2 for use in an adequate vaccine. This can be understood since this subunit, in a circulatory system, shows up the same way as the virus itself, essentially differing in the fact that the DNA and non-structural proteins are not present inside the capsid.
In the art several vaccines against PCV2 are known and commercially available.
Porcilis® PCV (available from MSD Animal Health, Boxmeer, The Netherlands) is a vaccine for protection of pigs against porcine circo virus type 2, for use in pigs from three weeks and older. When given as a two-shot (two dose) vaccine, the duration of immunity (DOI) is 22 weeks, almost completely covering the fattening period of pigs. The vaccination may lead to hyperthermia and other systemic reactions.
Ingelvac CicroFlex® (available from Boehringer Ingelheim, Ingelheim) is a vaccine for protection of pigs against porcine circo virus type 2, for use in pigs from two weeks and older. When given as a one-shot (one dose) vaccine, the DOI is 17 weeks. The vaccination may lead to hyperthermia and on a rare occasion in anaphylactic reactions. Circovac® (available from Merial, Lyon, France) is a vaccine for protection of pigs against porcine circo virus type 2, for use in pigs three weeks and older. When given as a two-shot vaccine, the DOI is only 14 weeks. The vaccination may lead to hyperthermia and other systemic reactions such as reduced feed intake.
Suvaxyn® PCV (available from Zoeitis, Capelle a/d IJssel, The Netherlands) is a vaccine for protection of pigs against porcine circo virus type 2, for use in pigs from three weeks and older. When given as a one-shot vaccine, the DOI is 19 weeks. The vaccination may lead to hyperthermia and other systemic reactions such as vomiting.
Other vaccines are described for example in WO2007/028823, WO 2007/094893 and WO2008/076915. None of them shows a DOI longer than as known from the commercial available vaccines.